1. Field of the Invention
The present invention relates to a color fog correction apparatus that corrects a color fog manifesting over, for instance, a photographic image that has become discolored after having been printed onto photographic printing paper or after having been stored over a long period of time on film, a photographic image obtained through a photographing operation performed under undesirable illumination conditions or exposure conditions and the like, and it also relates to a machine-readable recording medium having an image color fog correction program recorded therein.
2. Description of the Related Art
A color fog may occur in a photographic image obtained through an image-capturing operation performed with a camera due to undesirable illumination conditions, incorrect exposure conditions or the like. A color fog may also occur when a photographic image printed on photographic printing paper has become discolored. Such a color fog may adversely affect the color tone of the photographic image, causing it to turn reddish or greenish. The undesirable phenomena regarding color of a photographic image described above are referred to as “color fog” in this specification.
A color-fogged image is corrected, for instance, by estimating the spectrum of the illuminating light and applying to the image a filter of a color that is complementary to the color of the illuminating light, by exposing the three colors separately over different lengths of time when printing the image onto photographic printing paper and thus adjusting the degrees of color development to achieve color correction or by performing exposure correction to adjust the volumes of data corresponding to the three colors during digital processing to achieve color correction in the prior art.
However, there is a problem with the method of color correction in the prior art achieved by estimating the color of the illuminating light and applying a filter to the image of a color that is complementary to the color of the illuminating light in that it is difficult to accurately estimate the characteristics of the illuminating light. In addition, even if the characteristics of the illuminating light are accurately determined, there is a problem in that it costs a great deal of money to provide complementary color filters. This cost-related problem is not limited to hardware filters. When employing software filters, too, the cost of measuring a plurality of illuminating lights by using a reference chart to create filter data corresponding to a plurality of light colors is significant.
In addition, the color correction method achieved through exposure correction, which utilizes filters and necessitates correct lengths of exposure time to be allowed for the three colors, is costly and requires a great length of time for processing.